Hello @Nutan_Ghatge,
Before entering in procedures, sorry to ask these basics:
What power supply do you use?
Is the plug correct? It must be 4.75 mm outer diameter with 1.7mm center pin (EIAJ-3 Compliant)
Do you have a video attached to the board?
Note: It is not necessary to press any switch to power on the dragonboard, just plug it.